The spatio-temporal analysis of the incidence of tuberculosis and the associated factors in mainland China, 2009-2015.

BACKGROUND: Tuberculosis is still one of the most infectious diseases in China. This study aimed to explore the spatio-temporal distribution of TB and the associated factors in mainland China from 2009 to 2015. METHODS: A Bayesian spatio-temporal model was utilized to analyse the correlation of socio-economic, healthcare, demographic and meteorological factors with the population level number of TB. RESULTS: The Bayesian spatio-temporal analysis showed that for the population level number of TB, the estimated parameters of the ratio of males to females, the number of beds in medical institutions, the population density, the proportion of the population that is rural, the amount of precipitation, the largest wind speed and the sunshine duration were 0.556, 0.197, 0.199, 29.03,0.1958, 0.0854 and 0.2117, respectively, demonstrating positive associations. However, health personnel, per capita annual gross domestic product, minimum temperature and humidity indicated negative associations, and the corresponding parameters were -0.050, -0.095, -0.0022 and -0.0070, respectively. CONCLUSIONS: Socio-economic, number of health personnel, demographic and meteorological factors could affect the case notification number of TB to different degrees and in different directions.

Spatio-temporal survey of small mammal-borne Trypanosoma lewisi in Cotonou, Benin, and the potential risk of human infection.

Human trypanosomoses are the sleeping sickness in Africa and Chagas disease in Latin America. However, atypical human infections by animal trypanosomes have been described, but poorly investigated. Among them, the supposed rat-specific T. lewisi was shown to be responsible for a few severe cases. In Africa, the scarcity of data and the null awareness about the atypical human trypanosomoses suggest that the number of cases may be higher that currently thought. Furthermore, T. lewisi is resistant to normal human serum and therefore a potential human pathogen. In order to document T. lewisi distribution and ecology, a qPCR- and 16DNA sequencing-based survey was conducted in 369 rodents from three urban districts of Cotonou city, Benin, during three different periods of the same year. Our study demonstrated very high prevalence (57.2%) even when considering only individuals identified as positive through DNA sequencing (39.2%). Black rats represented the most dominant as well as the most T. lewisi-parasitized species. No difference was retrieved neither between seasons nor districts, suggesting a large infestation of rodents by trypanosomes throughout the year and the city. Our results suggest that conditions are gathered for rat to human transmission of T. lewisi in these socio-environmentally degraded urban areas, thus pointing towards the rapidly urbanizing Abidjan-Lagos corridor as a region at particular risk.

Integrative taxonomic approach of trypanosomes in the blood of rodents and soricids in Asian countries, with the description of three new species.

Trypanosoma lewisi (Kinetoplastea: Trypanosomatida: Trypanosomatidae) with a cosmopolitan distribution is the type species of the subgenus Herpetosoma, which includes ca. 50 nominal species isolated mainly from rodents. Since members of Herpetosoma in different host species have an almost identical morphology of bloodstream forms, these trypanosomes are referred to as 'T. lewisi-like', and the molecular genetic characterization of each species is necessary to verify their taxonomy. In the present study, we collected blood samples from 89 murid rodents of 15 species and 11 soricids of four species in Indonesia, Philippines, Vietnam, Taiwan, and mainland China for the detection of hemoprotozoan infection. T. lewisi and T. lewisi-like trypanosomes were found in the blood smears of 10 murid animals, which included Bandicota indica (two rats), Rattus argentiventer (one rat), and Rattus tiomanicus (two rats) in Indonesia; Rattus rattus (one rat) in the Philippines; and Niviventer confucianus (four rats) in mainland China. Furthermore, large- or medium-sized non-T. lewisi-like trypanosomes were detected in two soricids, Crocidura dracula in Vietnam and Anourosorex yamashinai in Taiwan, respectively. Molecular genetic characterization of the small subunit (SSU) ribosomal RNA gene (rDNA) and glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) gene indicated that the trypanosomes from all the murid hosts had identical SSU rDNA or gGAPDH gene nucleotide sequences except for those in N. confucianus in mainland China. These N. confucianus-infecting trypanosomes also showed several unique morphological features such as smaller bodies, anteriorly positioned nuclei, and larger rod-shaped kinetoplasts when compared with T. lewisi trypomastigotes. Trypanosoma (Herpetosoma) niviventerae n. sp. is erected for this new species. Similarly, based on morphological and molecular genetic characterization, Trypanosoma sapaensis n. sp. and Trypanosoma anourosoricis n. sp. are proposed for the trypanosomes in C. dracula in Vietnam and A. yamashinai in Taiwan, respectively. More effort directed toward the morphological and molecular genetic characterization of the trypanosomes of rodents and soricids is required to fully understand the real biodiversity of their hemoflagellates.

Leishmania major and Trypanosoma lewisi infection in invasive and native rodents in Senegal.

Bioinvasion is a major public health issue because it can lead to the introduction of pathogens in new areas and favours the emergence of zoonotic diseases. Rodents are prominent invasive species, and act as reservoirs in many zoonotic infectious diseases. The aim of this study was to determine the link between the distribution and spread of two parasite taxa (Leishmania spp. and Trypanosoma lewisi) and the progressive invasion of Senegal by two commensal rodent species (the house mouse Mus musculus domesticus and the black rat Rattus rattus). M. m. domesticus and R. rattus have invaded the northern part and the central/southern part of the country, respectively. Native and invasive rodents were caught in villages and cities along the invasion gradients of both invaders, from coastal localities towards the interior of the land. Molecular diagnosis of the two trypanosomatid infections was performed using spleen specimens. In the north, neither M. m. domesticus nor the native species were carriers of these parasites. Conversely, in the south, 17.5% of R. rattus were infected by L. major and 27.8% by T. lewisi, while very few commensal native rodents were carriers. Prevalence pattern along invasion gradients, together with the knowledge on the geographical distribution of the parasites, suggested that the presence of the two parasites in R. rattus in Senegal is of different origins. Indeed, the invader R. rattus could have been locally infected by the native parasite L. major. Conversely, it could have introduced the exotic parasite T. lewisi in Senegal, the latter appearing to be poorly transmitted to native rodents. Altogether, these data show that R. rattus is a carrier of both parasites and could be responsible for the emergence of new foci of cutaneous leishmaniasis, or for the transmission of atypical human trypanosomiasis in Senegal.

Predictors of Trypanosoma lewisi in Rattus norvegicus from Durban, South Africa.

This study investigated associations between Trypanosoma lewisi and Xenopsylla cheopis, a common cyclical vector of T. lewisi; Polyplax spinulosa, a reported mechanical vector; and Laelaps echidnina and Laelaps lamborni, 2 rodent mites of Rattus norvegicus in Durban, South Africa. In total, 379 R. norvegicus individuals were live-trapped at 48 sites in 4 locality types around Durban during a 1-yr period. Rats were euthanized, cardiac blood was taken to check for hemoparasites, and ectoparasites were removed for identification. Parasite species richness was higher in pups (2.11) and juveniles (1.02) than adults (0.87). Most rats in the study harbored 1 or 2 of the 5 parasites surveyed. Rats with trypanosomes and fleas were more prevalent in the city center and harbor, where juveniles were most affected. Rats with lice were more prevalent in informal settlements and urban/peri-urban areas, where pups had the highest infestations. There was a significant positive association between rats with fleas and trypanosomes and a negative association between rats with lice and trypanosomes. Location and rat age were significant predictors of T. lewisi, X. cheopis, and P. spinulosa. Mites showed no strong association with trypanosomes. Ectoparasite associations are possibly habitat and life-cycle related. We conclude that Durban's city center, which offers rats harborage, an unsanitary environment, and availability of food, is a high-transmission area for fleas and trypanosomes, and consequently a potential public health risk.

Landscape epidemiology in urban environments: The example of rodent-borne Trypanosoma in Niamey, Niger.

Trypanosomes are protozoan parasites found worldwide, infecting humans and animals. In the past decade, the number of reports on atypical human cases due to Trypanosoma lewisi or T. lewisi-like has increased urging to investigate the multiple factors driving the disease dynamics, particularly in cities where rodents and humans co-exist at high densities. In the present survey, we used a species distribution model, Maxent, to assess the spatial pattern of Trypanosoma-positive rodents in the city of Niamey. The explanatory variables were landscape metrics describing urban landscape composition and physiognomy computed from 8 land-cover classes. We computed the metrics around each data location using a set of circular buffers of increasing radii (20m, 40m, 60m, 80m and 100m). For each spatial resolution, we determined the optimal combination of feature class and regularization multipliers by fitting Maxent with the full dataset. Since our dataset was small (114 occurrences) we expected an important uncertainty associated to data partitioning into calibration and evaluation datasets. We thus performed 350 independent model runs with a training dataset representing a random subset of 80% of the occurrences and the optimal Maxent parameters. Each model yielded a map of habitat suitability over Niamey, which was transformed into a binary map implementing a threshold maximizing the sensitivity and the specificity. The resulting binary maps were combined to display the proportion of models that indicated a good environmental suitability for Trypanosoma-positive rodents. Maxent performed better with landscape metrics derived from buffers of 80m. Habitat suitability for Trypanosoma-positive rodents exhibited large patches linked to urban features such as patch richness and the proportion of landscape covered by concrete or tarred areas. Such inferences could be helpful in assessing areas at risk, setting of monitoring programs, public and medical staff awareness or even vaccination campaigns.

Diagnosis and genetic analysis of the worldwide distributed Rattus-borne Trypanosoma (Herpetosoma) lewisi and its allied species in blood and fleas of rodents.

Trypanosoma (Herpetosoma) lewisi is a cosmopolitan parasite of rodents strongly linked to the human dispersal of Rattus spp. from Asia to the rest of the world. This species is highly phylogenetically related to trypanosomes from other rodents (T. lewisi-like), and sporadically infects other mammals. T. lewisi may opportunistically infect humans, and has been considered an emergent rat-borne zoonosis associated to poverty. We developed the THeCATL-PCR based on Cathepsin L (CATL) sequences to specifically detect T. (Herpetosoma) spp., and assess their genetic diversity. This method exhibited high sensitivity using blood samples, and is the first molecular method employed to search for T. lewisi in its flea vectors. THeCATL-PCR surveys using simple DNA preparation from blood preserved in ethanol or filter paper detected T. lewisi in Rattus spp. from human dwellings in South America (Brazil and Venezuela), East Africa (Mozambique), and Southeast Asia (Thailand, Cambodia and Lao PDR). In addition, native rodents captured in anthropogenic and nearby human settlements in natural habitats harbored T. (Herpetosoma) spp. PCR-amplified CATL gene fragments (253bp) distinguish T. lewisi and T. lewisi-like from other trypanosomes, and allow for assessment of genetic diversity and relationships among T. (Herpetosoma) spp. Our molecular surveys corroborated worldwide high prevalence of T. lewisi, incriminating Mastomys natalensis as an important carrier of this species in Africa, and supported its spillover from invader Rattus spp. to native rodents in Brazil and Mozambique. THeCATL-PCR provided new insights on the accurate diagnosis and genetic repertoire of T. (Herpetosoma) spp. in rodent and non-rodent hosts, revealing a novel species of this subgenus in an African gerbil. Phylogenetic analysis based on CATL sequences from T. (Herpetosoma) spp. and other trypanosomes (amplified using pan-trypanosome primers) uncovered rodents harboring, beyond mammal trypanosomes of different subgenera, some species that clustered in the lizard-snake clade of trypanosomes.

Resistance to normal human serum reveals Trypanosoma lewisi as an underestimated human pathogen.

Human-infectious trypanosomes such as Trypanosoma cruzi, T. brucei rhodesiense, and T. b. gambiense can be discriminated from those only infecting animals by their resistance to normal human serum (NHS). These parasites are naturally resistant to trypanolysis induced by the human-specific pore-forming serum protein apolipoprotein L1 (ApoL-1). T. lewisi, a worldwide distributed parasite, has been considered as rat-specific and non-pathogenic to the natural hosts. Here we provide evidence that 19 tested T. lewisi isolates from Thailand and China share resistance to NHS. Further investigation on one selected isolate CPO02 showed that it could resist at least 90% NHS or 30 µg/ml recombinant human ApoL-1 (rhApoL-1) in vitro, in contrast to T. b. brucei which could not survive in 0.0001% NHS and 0.1 µg/ml rhApoL-1. In vivo tests in rats also demonstrated that this parasite is fully resistant to lysis by NHS. Together with recent reports of atypical human infection by T. lewisi, these data allow the conclusion that T. lewisi is potentially an underestimated and thus a neglected human pathogen.

Comparison between Quantitative Buffy Coat (QBC) and Giemsa-stained Thin Film (GTF) technique for blood protozoan infections in wild rats.

The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared to determine the sensitivity and specificity of the technique in detecting blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia. A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii, Rattus exulans and Rattus argentiventer) were screened using both techniques and successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%) compared to Quantitative Buffy Coat method (38.9%) with overall detection technique sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at 76.6%. Statistical analysis proved that GTF technique was significantly more sensitive in the detection of blood protozoan infections in the rodent population compared to QBC (p<0.05).

On opportunist infections by Trypanosoma lewisi in humans and its differential diagnosis from T. cruzi and T. rangeli.

Trypanosoma lewisi is a cosmopolitan species originally found in Rattus spp., being nonpathogenic, host-restricted, and transmitted by rat fleas. This species has been recorded as an opportunist blood parasite of human beings mainly in Asia, with a case in Africa. In Brazil, this species was recently recorded in captive monkeys. As T. lewisi can share vertebrate hosts both with Trypanosoma rangeli and Trypanosoma cruzi, some markers for the differential diagnosis of these species were examined and discussed herein. The identification of T. lewisi was based on morphological features of bloodstream stages at the initial phase of infection in mammals, isoenzyme electrophoresis at the MDH locus, and PCR products of kinetoplast DNA (kDNA) minicircles using the primers TC121/TC122.

Epidemiology of blood parasitic infections in the urban rat population in peninsular Malaysia.

A total of 719 wild rats were captured from four localities representing the west (Kuala Lumpur), east (Kuantan), north (Georgetown) and south (Malacca) to determine the diversity of blood protozoan from the urban wild rat population in peninsular Malaysia. Five rat species were recovered with Rattus rattus diardii being the most dominant species, followed by Rattus norvegicus, Rattus exulans, Rattus annandalei and Rattus argentiventer. Two blood protozoan species were found infecting the rodent population namely, Plasmodium sp. (42.1%) and Trypanosoma lewisi (25.0%). This study reports the presence of Plasmodium sp. for the first time in the rodent population in Malaysia. Two main intrinsic factors were identified affecting the parasitic infections. Trypanosoma lewisi infections were influenced by host age and sex with infections observed higher in male and juvenile rats meanwhile Plasmodium sp. infections were observed almost similar in both sexes. However, infections were higher in sub-adult rats.

Detection of Trypanosoma lewisi from wild rats in Southern China and its genetic diversity based on the ITS1 and ITS2 sequences.

Trypanosoma lewisi has widely been considered as a non-pathogenic rat trypanosome. However, more and more cases of humans infected with T. lewisi have been reported around the world, indicating that it can infect humans in some undetermined circumstances. Quick and sensitive diagnosis of infection by T. lewisi is important for both treatment of patients and epidemiological studies of this parasite. In this paper, three methods i.e. wet blood smear (diagnosis by microscopy), PCR and LAMP were used to detect T. lewisi from 238 wild rats (Rattus norvegicus) collected from the field in Huadu, Guangdong province, China. Infection rates of these samples detected by the 3 methods was 6.7% (16/238), 12.6% (30/238), and 18.9% (45/238), respectively. LAMP could detect all samples shown positive by microscopical observation of wet smear and by single PCR indicating good potential for application in the detection of T. lewisi. So far as we know, this is the first report of the LAMP method being used to detect T. lewisi in wild rats. The specific T. lewisi LAMP primers were able to amplify the target fragment from the genomic DNA of 19 T. lewisi strains isolated from Huadu, Guangdong province (n=16), Changchun, Jilin province of China (n=1) and from Thailand (n=2). Based on the analyses of ITS1 (internal transcribed spacer 1) and ITS2 sequences, these 19 strains show a very close genetic relationship with over 96-97% similarity to the other corresponding sequences of T. lewisi published in Genbank. Phylogenetic trees of the species in the subgenus Herpetosoma were constructed, based on the ITS1 and ITS2 sequences, and these results also indicate that they are closely related and in the same clade.

Specific primers for PCR amplification of the ITS1 (ribosomal DNA) of Trypanosoma lewisi.

Trypanosoma lewisi is a mild or non-pathogenic parasite of the sub-genus Herpetosoma transmitted by fleas to rats. In a previous study we described pan-trypanosome specific primers TRYP1 which amplify the ITS1 of ribosomal DNA by hybridizing in highly conserved regions of 18S and 5.8S genes. These primers proved to be useful for detecting T. lewisi DNA in laboratory rats, but a recent large scale survey in wild rodents demonstrated a lack of specificity. In the present study, we designed and evaluated mono-specific primers LEW1S and LEW1R, for the detection and identification of T. lewisi by a single-step PCR. These primers were designed inside the highly variable region of the ITS1 sequence of T. lewisi ribosomal DNA. The product size of 220 bp is specific to T. lewisi. The sensitivity limit was estimated between 0.055 and 0.55 pg of DNA per reaction, equivalent to 1-10 organisms per reaction. All the PCR products obtained from 6 different T. lewisi isolates were more than 98% similar with each other and similar to the sequences of T. lewisi already published in Genbank. All DNA of 7 T. lewisi stocks from China gave the specific 220 bp product. We showed that LEW1S and LEW1R primers enabled sensitive detection and identification of T. lewisi infection in laboratory and wild rats. This assay is recommended for monitoring T. lewisi infections in rat colonies or for studying infections in the wild fauna. An absence of cross reaction with human DNA means that these primers can be used to investigate atypical trypanosome infections in humans. Given the risk of T. lewisi infection in human, we believe that these primers will be beneficial for public health diagnosis and rodents investigation programmes.

The occurrence and ultrastructure of Trypanosoma (Herpetosoma) lewisi (Kent, 1880) Laveran and Mesnil, 1901, the parasite of rats (Rattus norvegicus) in Poland.

This study reports the light and electron microscopic examination of Trypanosoma (Herpetosoma) lewisi (Kent, 1880) Laveran and Mesnil, 1901, isolated from rats (Rattus norvegicus) from Poland. Bloodstream trypomastigotes were identified morphometrically from 100 specimens collected from three naturally infected rats Rattus norvegicus. Body length ranged from 15.45-23.64 microm and width from 1.3-2.32 microm while the free flagellum was 8.1 microm long. Electron microscopic study of bloodstream trypomastigotes exhibited typical ultrastructural features similar to those of other stercorarian trypanosomes. The presently determined morphological data have been compared with those provided by other authors.

Diagnosis of a Trypanosoma lewisi-like (Herpetosoma) infection in a sick infant from Thailand.

Trypanosomes were observed in a peripheral blood smear from a 45-day-old Thai infant displaying fever, anaemia, cough and anorexia. Human trypanosomiasis is not endemic to Thailand, so parasite identification was undertaken to determine likely sources of the infection. Several morphological parameters of the trypanosomes were similar to those of Trypanosoma evansi and statistically different from those of Trypanosoma lewisi-like parasites from a naturally infected indigenous rat. However, duplicate PCR assays with primers flanking trypanosome rRNA internal transcribed spacer 1 (ITS1) resulted in amplicons of approximately 623 bp that corresponded to the expected size for T. lewisi-like parasites. The ITS1 sequence from the infant's blood was 98 and 49 % identical to T. lewisi and T. evansi sequences, respectively. Based on molecular results, it was concluded that the infant was infected with a T. lewisi-like (Herpetosoma) species.

Infection by trypanosomes in marsupials and rodents associated with human dwellings in Ecuador.

Small mammals trapped in domestic and peridomestic environments of rural Ecuador were screened for trypanosome infection by direct microscopy and hemoculture. Identification of species of trypanosomes was then performed by morphological characteristics and by polymerase chain reaction (PCR) assays. Of 194 animals collected, 15 were positive for infection (7.73%). Eight (4.12%) were infected with Trypanosoma cruzi (1 of 33 Didelphis marsupialis; 7 of 61 Rattus rattus). Eleven R. rattus (18.03%) harbored T. lewisi, 5 of which presented mixed infections with T. cruzi. Additionally, 1 of 3 Oryzomys xanthaeolus was infected with T. rangeli. No trypanosome infection was detected in Philander opossum (n = 1), Mus musculus (n = 79), Rattus norvegicus (n = 8), Akodon orophilus (n = 4), Sigmodon peruanus (n = 3), or Proechimys decumanus (n = 2). Many of the isolates belong to T. cruzi, the causative agent of Chagas disease, and R. rattus had the highest prevalence. Because of its abundance in the study areas, this species is considered an important reservoir for Chagas disease. This is the first report of T. lewisi and T. rangeli in Ecuador. This study is also the first to describe natural mixed infections of T. cruzi-T. lewisi.

Prevalence of Trypanosoma lewisi in Rattus norvegicus from Belo Horizonte, State of Minas Gerais, Brazil.

From April 1984 to March 1985, a Trypanosoma lewisi prevalence of 21.7% was found in 429 Rattus norvegicus trapped in Belo Horizonte, State of Minas Gerais, Brazil. The infection rates were higher in male and young rats and could be attributed to ecological and behavioral factors. T. lewisi was observed in rats measuring between 60 and 250 mm. Data about monthly T. lewisi infections throughout the year are presented for the first time in Brazil, with the highest prevalences observed in the warm-rainy season (October to March).